Generation of heralded single photons beyond 1100 nm by spontaneous four-wave mixing in a side-stressed femtosecond laser-written waveguide

TL;DR

This paper reports the development of a monolithically integrated, femtosecond laser-written glass waveguide that generates heralded photon pairs with over 300 nm wavelength separation, suitable for quantum photonics applications.

Contribution

It introduces a novel side-stressed waveguide with high birefringence and low loss, enabling efficient generation of widely separated photon pairs beyond 1100 nm.

Findings

Birefringence of 1.64×10⁻⁴ achieved in the waveguide

Photon pairs with 300 nm wavelength separation generated at >5.05×10⁶/s

Photon pairs exhibit strong non-classical correlations

Abstract

We demonstrate a monolithically integrable heralded photon source in a femtosecond laser direct written glass waveguide. The generation of photon pairs with a wide wavelength separation requires a concomitant large birefringence in the normal dispersion regime. Here, by incorporation of side-stress tracks, we produce a waveguide with a birefringence of $1.64\times~10^{-4}$ and propagation loss as low as 0.21 dB/cm near 980~nm. We measure photon pairs with 300~nm wavelength separation at an internal generation rate exceeding $5.05\times10^6$/s. The second order correlations indicate that the generated photon pairs are in a strongly non-classical regime.